Aircraft need to produce varying levels of lift for take-off, landing and cruise. A combination of wing leading and trailing edge devices are used to control the wing coefficient of lift. The leading edge device is known as a slat. On larger aircraft there may be several slats spaced along the wing edge. During normal flight the slats are retracted against the leading edge of the wing. However, during take-off and landing they are deployed forwardly of the wing so as to vary the airflow across and under the wing surfaces. The slats usually follow an arcuate or curved path between their stowed and deployed positions. By varying the extent to which the slat is deployed along said path, the lift provided by the wing can be controlled.
An assembly is required to support and guide movement of a slat between stowed and deployed positions.
A slat support and deployment assembly has already been described in the Applicant's own earlier application No. EP2433863, the entire content of which is incorporated herein by reference.
The aforementioned application refers to a support assembly for deployment and retraction of an aero surface from an aircraft that includes a guide track, a primary support arm having one end coupled to a carriage mounted on the track such that the primary support arm is rotatable relative to the carriage about multiple axes, and a control arm having one end coupled to the primary support arm and a second end pivotably attachable to a fixed support forming part of the structure of the aircraft. The assembly is configured such that, when the carriage is driven along the guide track, the control arm causes the primary support arm to pivot about said multiple axes to deploy and/or retract an aero surface pivotally attached to an opposite end of the primary support member along an arcuate path.
A more detailed description of the structure and function of the slat deployment assembly will now be described with reference to FIGS. 1 and 2, which have been taken from our earlier application identified above.
Referring primarily to FIG. 1, the assembly 1 comprises a carriage 2 having a body 3 mounted on an elongate track 4. The track 4 is rigidly attached to the wing structure of an aircraft so that it remains stationary relative to a rib 5 forming part of the wing structure. The track 4 has a flange 6 that may be placed against part of the wing structure. Holes (not shown) may extend through the flange 6 to allow bolts or other conventional fasteners to be inserted therethrough to facilitate attachment of the track 4 to the wing structure. The track 4 also has a carriage mounting portion 7 attached to the flange 6 via a thinner, necked region 8.
A rotatable threaded drive shaft 9 extends along the track 4 within a recess 10 in the track 4 and threadingly engages within a drive coupling portion 11 of the carriage 2 that extends into the recess 10 such that, when the threaded shaft 9 rotates, in response to rotation of a drive motor (not shown) drivingly coupled to the shaft 9, the carriage 3 slides along the elongate track 4, its direction depending on the direction of rotation of the shaft 9.
The carriage 3 is supported on the track 4 by a pair of upper and lower bearings (not shown) each inserted into a recess in the carriage 3.
The carriage 3 has spaced parallel wall portions 12 extending from the body 3 between which is mounted an axle 13 having a generally square-shaped cross-section. The axle 13 is mounted to the carriage 3 for rotation about its longitudinal axis ‘H’ relative to the carriage 3.
A primary support arm 14 has a pair of upper and a pair of lower arm portions or legs 14a, 14b. Each of the upper arm portions 14a and each of the lower arm portions 14b extend from a cylindrical mounting boss 15a, 15b located at one end of the upper and lower arm portions 14a, 14b. The axle 13 locates in the space between these mounting bosses 15a, 15b at the end of each arm portion 14a, 14b and the primary support arm 14 is coupled to the axle 13 by a pin (not shown) that extends through the axle 13 and a hole 16 in each mounting boss 15a, 15b, thereby pivotally connecting the primary support arm 14 to the axle 13 for rotation about an axis ‘I’, which is at 90 degrees to axis ‘H’. The pivotal connection of the axle 13 to the carriage 3 for rotation about axis ‘H’ and the pivotal connection of the primary support arm 14 to the axle 13 for rotation about axis ‘I’ together form a universal joint to enable free movement of the primary support arm 14 relative to the carriage 3 as the carriage 3 slides along the guide track 4.
The primary support arm 14 has a cylindrical boss 17 with an aperture 18 at its opposite end to receive a pin (not shown) so as to pivotally couple the primary support arm 14 to a slat about axis J-J, as will become apparent from a description of the preferred embodiments of the present invention.
A secondary support or control arm 18 is coupled to the primary support arm 14 between opposite ends of the primary support arm 14 via a cylindrical barrel rotating in an annulus with a slot with the arm pivoting about the pin to form a universal joint assembly 19. The primary support arm portions 14a, 14b each have an intermediate mounting boss 20a, 20b positioned between each of the upper arm portions 14a and each of the lower arm portions 14b midway along the length of the primary support arm 14. Each of the mounting bosses 14a, 14b are parallel to and spaced from each other. A shaft 21 is connected to and extends between the intermediate mounting bosses 20a, 20b and has a central part-spherical region that forms a male bearing seat or surface. One end of the secondary control arm 18 that connects to the primary support arm 14 has a collar 22 that defines an inner or female part spherical bearing surface that locates around, and mates with, the part spherical bearing surface formed on the shaft 21, so that the control arm 18 can rotate relative to the primary support arm 14 in all directions.
The control arm 18 of the invention comprises support arm portions 23 which diverge at an angle away from the collar 22 and, from each other. Each support arm portion 23 terminates in an annular member 24 that is received within an opening 25 in the rib 5. A pin (not shown) is associated with each annular member 24 and locates in the rib 5 so that it passes through each annular member 24 to facilitate pivotal connection of each annular member 24 to the rib 5 for rotation of the secondary control member 18 about an axis K.
Axes I and J at opposite ends of the primary support member 14 are parallel to each other and remain so during deployment and retraction of the slat. However, it will be noted that axis K extending through the annular members 24 is at an angle relative to axes I and J i.e. it is displaced through a compound angle in both directions so that it is rotated about the longitudinal axis H of the axle 13 as well as being displaced through an angle such that it not perpendicular to the longitudinal axis H. This arrangement produces an arcuate path to the free end of the primary support arm 14 when the carriage 3 slides laterally along the track 4 and the primary support arm 14 rotates about axes H and I.
To deploy a slat coupled to the primary support arm 14, the motor is driven to rotate the threaded shaft 9 so that the carriage 3 moves in a first direction S along the track 4. As the carriage 3 moves, the primary support arm 14 rotates relative to the carriage 3 about the axis I, and also relative to the control arm 18 about the spherical joint 19. At the same time, the axle 13 rotates about its axis H such that the primary support member 14 also moves downwardly, the spherical ball joint 19 between the primary and secondary support members 14, 18 allowing this movement. As a result, the free end of the primary support arm 14 follows an arcuate path in an outward direction away from the track 4, i.e. in the direction of arrow ‘T’ in FIG. 1.
To retract the slat, the direction of rotation of the threaded shaft 9 is reversed so that the carriage 3 moves along the track 4 in the opposite direction thereby causing the primary support member 14 to follow a return arcuate path back towards the track 4.
It will be appreciated that at least two slat deployment assemblies are required to effectively support and control the deployment of each slat. The slat support assemblies are spaced from each other in a direction along the length of the wing in order to provide adequate support for, and controlled deployment of, the slat along its entire length. FIG. 2 shows such an arrangement, with a slightly modified slat and carriage assembly, each of which are attached to a slat 26. Despite this modification, the principle and operation described with reference to FIG. 1 remains the same.
During assembly, it is important to ensure that when a slat is coupled to the slat support assemblies, the slat is properly aligned with the wing and, in particular, that the upper trailing edge of the slat sits flush with, and against, the leading edge of the wing when the slat is in a closed or withdrawn position, such as during level flight.
It is also apparent that there may be slight differences in the deployment path followed by each slat support assembly during deployment, caused by build tolerances, misalignment or uneven wear between slat support assemblies. This can result in undue stress being placed on the slat if one or more of the slat support assemblies coupled to the same slat is effectively attempting to drive the slat in a slightly different direction or into a different position between its stowed and deployed positions.
The effects of wing bending must also be considered so that no undue stress is placed on the slat during deployment or retraction.
In one embodiment of the present invention, it has been assumed that the slat itself is sufficiently flexible to absorb any misalignments caused by build tolerances or uneven support assembly deployment, as well as withstand any deflection caused by wing bending. This embodiment therefore only provides a slat support assembly coupling that is provided with means to enable fine-adjustment of the position of the slat relative to the slat support assembly and so relative to the wing to which the slat support assembly is mounted, so that the shut-line between the trailing edge of the slat and the leading edge of the wing to which the slat is mounted can be precisely adjusted during assembly to ensure that the upper surface of the slat and the upper surface of the wing lie flush with each other when the slat is in its stowed position.
In another, preferred embodiment of the invention, there is provided a slat support coupling that has a construction that accommodates and adjusts for any misalignments and wing bending deflections, so that the slat itself experiences only minimal stress.
From the foregoing, it will be appreciated that the present invention seeks to overcome or alleviate one or more of the problems referred to above.